The site where three Chinese nationals illegally mined iron in the central province of Thua Thien-Hue. Photo: Bui Ngoc Long

Police in Vietnam's central province of Thua Thien-Hue have asked immigration authorities to expel five Chinese tourists for working and doing business illegally.

The foreigners were also fined VND75 million (nearly US$3,500) in total, Nguyen Van Thanh, a spokesman for the police, said Friday.

Three of them -- Liang Qingxiang, 55, Chen Wubin, 52, and Liang Yongcai, 31 -- entered Vietnam on February 25 and had since frequented an iron mining site in Nam Dong District for testing samples.

On March 20 they began mining iron at another place in collaboration with a few locals.

Local authorities raided the area, which is not licensed for mining, earlier this month and found they had excavated nearly 2,000 square meters of land, Nguyen Dac Truong, deputy director of the province's environment department, said.

By then they already reached the laterite soil layer that is rich in iron oxide, he said.

The police said they seized mining equipment and tools that the Chinese had brought into Vietnam for investigation.

Elsewhere, Cao Qi, 27, and Yang Renhua, 34, were found working as mechanical experts at Thuong Lo Hydropower Company also in Nam Dong without work permits.

They had been sent over by a Chinese hydropower plant, which is a partner of Thuong Lo.